Control apparatus



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Oct, l0, 1950 CONTROL APPARATUS 10 Sheets-Sheet 8 Filed arch 16, 1944 Gttcrneg J. F. scHoEPPEL a-rAL 2,524,998

comm. APPARATUS Oct. 10, 1950 19 Sheets-Sheet 9 Filed March 16, 1944 www t, In

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cumul. APPARATUS Filed latch 16, 1944 10 Sheets-Sheet 10 Patented Oct. 10, 1950 CONTROL APPARATUS John F. Schoeppel and Albert Palya, Minneapolis,

Minn.,

Regulator Company, corporation of Delaware assignors to Minneapolis-Honeywell Minneapolis, Minn.. a

Application March 16, 1944, Serial No. 526,806

zs claims. l

This invention relates to control apparatus generally and more specifically to means for controlling the course of an aircraft and the azimuth of a. line of sight in the performance of bomblng operations.

The problem in bombing from an aircraft is to release a projectile from a plane, moving in a given direction at a given speed with respect to a target and at given altitude above the target, at such a point in space and time that the bomb having fallen from the releasing craft impacts upon the target. i

The field of bombsights is substantially comprehended in two main subdivisions-synchronous bombsights and point-of-impact bombsights. A synchronous sight, as is well known, includes mechanism whereby a line of sight can be moved with respect to the plane in which it is carried at such speeds and in such directions as to make the target appear stationary in the field of the sight during bombing runs at various altitudes and airspeeds. A point-of-impact sight, on the other hand, is directed at all times toward the point where a projectile, if released at the instant of observation, would impactthe ground.

Two principal factors enter into the performance of the bombing run. One is determination of the range, that is, the distance along the course of the craft between the target and the point at which the projectile should be released. The other is determining the proper heading of the craft, the wind velocity being considered, to give the proiectile such an initial direction when released that it will pursue a path in its fall ending directly upon the target. be referred to herein as the range factor in bombing and the latter as the azimuth factor. The present invention relates solely to the azimuth factor.

In both synchronizing and point-of-impact bombing, it is necessary that the plane be moving in a certain direction at the point of release of the bomb for the bomb to land on the target even if the rance factor is correct. Furthermore. in both synchronizing and point-of-impact bombsights, means are provided for adjusting the right in azimuth to take into account the vary- Pr: drift angles occurring as a result of varying vind factors. The drift angle. it is understood. i* the angle between the ground path of the craft and its heading: In the absence of wind having components normal to the course of the craft. the drift angle is zero. When flying in a Y"ind having a component normal to the course of the craft, the nose of the craft must be pointed The former will in a direction other than directly toward the target if the ground path of the plane is to be directly through the target. The azimuth factor in a synchronizing bombsight has for its purpose to so direct the line of sight of the bombardier that when the target appears to remain on the crosshairs of the sight a proper drift angle has been established, and the plane is following such a course that a projectile released at the proper moment will impact the target. In a point-ofimpact sight. when the target appears to be moving along the range cross hair without deviation to either side, the same situation exists.

It is understood that some form of communication between the bombardier and the pilot of the craft must be provided, so that the observations of the bombardier may be translated into maneuvers of the craft effective to place it on the deslred course. Direct telephone connections and pilot-directing instruments have both been employed for this purpose. particularly with aircraft which are flown manually by the pilot. However, in modern bombers where an automatic flight control system is provided for the purpose. as far as bombing is concerned, of maintaining a stable platform for the bombsight, it is obviously more efficient to arrange some sort of mechanism whereby, in the operation of the bombsght, the bombardier also operates control surfaces of the aircraft. Such bombsights are known.

In the azimuth factor of bombing two principal procedures have been established. The rst or rate procedure includes means for altering the azimuth of the bombsight by means of an azimuth knob operated by the bombardier, the rate at which the azimuth is changed depending upon the degrees of displacement of the azimuth knob. The second or "dsplacement procedure comprises altering the azimuth of the sight by the use of a drift angle knob, the magnitude of the displacement rather than its rate being determined by the angular displacement of the drift angle knob.

An object of our invention is to4 provide an efficient accurate combination of a bombsight, a directional gyroscope, and a night control system in which the functions of the various components are coordinated in a novel fashion.

Another object of our invention is to provide such a combination including a pair of improved telemetric systems in which a motor energized by the first system is operative to vary the heading of the craft in which the flight control system is installed and the motor energized by the sec.- ond system is operative to vary the azimuth of the line oi' sight of the bombsight with respect to the craft, together with first manual means for affecting the balance of the irst telemetric system and second manual means for independently aiecting the balance of both telemetric systems simultaneously and with means whereby deviation of the aircraft from a predetermined course may independently affect the balance of the second telemetric system.

Another object of our invention is to provide a control attachment adapted to be assembled mechanically to a bombsight and comprisingr a pair of improved potentiometers together with iirst manual means rotating` the resistance elements of the potentlometers as a unit, second manual means rotating the contact portion of one of the potentiometer-s and further a motor actuated means for rotating the contact portion of the other potentiometer: means also being provided ior coupling the above mntioned motor with a driven member in the bombsight, for conducting electrical energy to the attachment, and for conducting electrical energy through the attachment and to the bombsight circuits under suitable supervisory control.

Yet another obiect of our invention is to provide means wherebv the course ci' a vehicle may be changed by operation of a remote control knob, the change being made at a constant rate, and through an angle proportional to the angular disnlacement of the control knob.

A further obiect of our invention is to provide, in course control apparatus regulated bv a directional gvroscnpe. rnotor means for va ryingthe normal relation between the directionalY gyroscope and the link joining it with the element actuating the course control member of the aircraft.

A further object of our invention is to provide a potentiometer. one portion of w-if:h is stabilized in space about an axis. whie the other portion is movable with respect thereto in accordance with the departure of a vehicle from a predetermined course.

A still further obiect of our invention is to provide means wherebv the azimuth of the line of sight of a bombsight, with respect to an aircraft, may be changed by the operation of a remote control knob, the change being made at a constant rate and through an angle proportional to the angular displacement of the control knob.

Further objects and advantages of our invention are set forth in the following descrirtion, taken with the accompanying drawings. and the novel features thereof are pointed out in the appended claims. The disclosure, however, is illustrative only and I may make changes in detail, especially in matters of shape, size, and arrangement of parts within the principle of the invention, to the full extent indicated by the broad general meanings of the terms in which the appended claims are expressed.

In the drawing:

Figure 1 is a schematic representation of the general system comprising the subject matter of our invention,

Figures 2 and 3 taken together disclose a complete electrical wiring diagram, schematic in parts, of our system,-together with the necessary sources of electrical energy, and utilizing circuits in the bombsight,

Figure 4 is a sectional view of a portion of a control attachment comprising a preferred ernbodiment of a portion of our inventionl Figure 5 is a sectional view of the remaining portion of the embodiment in Figure 4,

Figure 6 is a side view of the device shown in Figure 4, a portion being broken away along thc line generally indicated by 6 8 in Figure 4 to disto disclose features of internal structure,

Figure 7 is a side view of a potentiometer particularly adapted for use in an embodiment of our invention, a portion being broken away for purposes of illustration,

Figure 8 is a view of the device shown in Figure 'l as seen from the right, portions also being broken away for purposes of illustration,

Figure 9 shows a slip ring as used in the potentiometer shown in Figure 6,

Figure l0 is a sectional view taken along line I-i 0 in Figure 9,

Figure 11 is a plan view of our motor drive attachment, certain parts being broken away for purposes of illustration,

Figure l2 is a sectional elevation of our motor drive attachment, taken along the line indicated by I2-I2 inFig. 11,

Figure 13 is an elevational view of our steering motor drive, more clearly disclosing certain features thereof, parts being broken away along a line generally indicated by |3l3 in Figure 11,

Figure 14 is a sectional view of a potentiometer adapted for cooperation with a directional stabilizer in the practice of our invention, together with adjacent parts of the stabilizer.

Referring now to Figure 1, it will be seen that an embodiment of our invention comprises a directional stabilizer indicated generally by reference numeral il, a bombsight indicated schematically by reference numeral I2, and a control attachment for coordinating and controlling the relationship between the bombsight and the directional stabilizer, generally indicated by reference numeral I3: suitable amplifiers are also required to energize various electrical elements comprised in the main units just recited.

Directional stabilizer Il comprises a gyroscope Il including a rotor energized in any convenient fashion for rotation at high speed about a generally horizontal spin axis which defines the stabilized azimuth axis of the plane. Gyroscope I4 is pivotally mounted in a gimbal ring i! which is rotatable about a normally vertical axis. A shaft I6 extends vertically from gyroscope Il: rigid upon shaft IB are a gear I1 and a clutch 2li,

and rotatable upon shaft IB is a housing!! which includes a locking arm 2| arranged to cooperate with -any suitable clamping mechanism, not shown, to lock member 22 to the craft, when this action is desired. It is clear that, arm 2l remaining unlocked, gyroscope il and gimbai ring i5 remain motionless with respect to the craft as long as the motion of the latter has the direction of the stabilized axis.

If the azimuth axis of the craft moves in a direction other than parallel to itself; that is, if the craft turns to the left or to the right, the gyroscopic rigidity imparted to shaft I6 simply causes the gimbal to remain fixed in space while the craft turns around it. However, a locking arm 2i is provided, on a housing 22 rotatably carried by shaft IB, for cooperating with any suitable clamping mechanism, not shown, to ilx member 22 against rotation about the axis of shaft I6.

Gyroscope Il is grounded as shown at 2l through its gimbal ring, and carries a movable contact 25 adapted to move over the resistance member 26 of a potentiometer indicated generalfollows.

ly at 21. Electrical connections are made to the ends of resistance member 26 as by conductors 36 and 3| and these conductors lead to an amplifier 32. According to the well known principles of gyroscope operation, any force applied about the axis of shaft I6 results, not in rotation of gimbal I5 about that axis, but in rotation of housing I4 about its axis in gimbal I5, moving contact 25 of potentiometer 21 upward or downward along winding 26, depending on the direction of action of the force and the direction of rotation of the gyro rotor: the degree of movement of contact 25 depends on the magnitude of the applied force.

Use is made of this movement of housing |4 through an amplifier 32 and a clutch means 36, as

A second shaft 33 is arranged for continuous rotation by a motor 34, and is reversibly connected to a shaft 35 through clutch means 36. Clutch means 36 provides a mechanism whereby energy of rotation of shaft 33 is transmitted to shaft 35 either directly or in reverse, depending on which of two solenoids is energized. In the absence of energization of either solenoid, no energy of rotation is transmitted to shaft 3-5. The latter shaft carries a gear 31 which is connected by suitable gearing 46 with gear I1 carried by shaft I6. Thus, it will be seen that rotation of shaft 35 in a counterclockwise direction is adapted to apply torque to shaft I6 also in a counterclockwise direction. Motor 34 is provided with energy for continuous operation as by conductors 38 and 39, the latter being grounded. Electrical conductors 4| and 42 and ground connections 43 and 46 are arranged for connecting the solenoids in clutch 36 with amplifier 32. The latter is provided with electrical energy from any suitable source as by conductors 44 and 45, the latter being grounded.

Amplifier 32 includes a center tapped resistor whose halves cooperate with the portions into which winding 26 is divided by contact 25 to comprise a Wheatstone bridge which is in balance when contact 25 is in the center of winding 26. For all other positions of contact 25, the bridge is unbalanced, and an alternating signal voltage derived from conductors 44 and 45 is supplied by the bridge, varying in amplitude with the displacement of contact 25 from the center Winding 26 and reversing in phase as contact 25 passes the center of windingr 26. The signal voltage is amplified and energizes on: or the other of the solenoids in clutch 36, depending on its phase compared with that of the source. Suitable ampliflers are well known in the art, and details of the structure of amplifier 32 are therefore not included in the present application.

The over-all function of this portion of our invention is therefore to cause application of torque to shaft 35 (refer now to Figure 1) in a first direction when gyroscope I4 tilts in a first direction, and in the opposite sense when the gyroscope tilts in the opposite direction.

Torque applied to shaft 35 is transmitted through gearing 40 to ring gear I1 and shaft I6. The force acting on shaft I6 is now reversed, and opposite precessive movement of contact 25 takes place, removing the signal from the amplifier when the shaft has been returned to its original position. Thus, the torque exerted on shaft I6 by link |21 is opposed, not directly by the rigidity of the gyroscope, but by the motor 34, which is for this reason referred to as the torque motor of the system although as a matter of fact it is con- Ill tinuously rotating, torque being obtained therefrom through slipping in clutches 36.

Means are provided whereby the course upon which the craft is stabilized by the gyroscope |4 may be changed at the will of the pilot. To accomplish this, -a worm wheel 23 is rotatably mounted on shaft I6 in frictional drive relation thereto.

Mounted on housing 22 for movement therewith around shaft I6 is a motor |32 having a shaft |33 carrying a worm |34. Worm |34 engages worm wheel 23 so that in the absence of rotation of shaft |33 worm wheel 23 is locked to housing 22, as previously mentioned. On rotation of shaft |33, however, relative rotation may take place between housing 22 and shaft I6 independent of this joint rotation, and the effect of the resultant movement of arm on control surface operator |3| is the same as a simi'ar movement of arm |30 due to operation of gyroscope I4, clutch means 20, and so forth. It is thus clear that by energize.- tion of motor |32 it is possible to cause the com trol surface operator to change the course of the craft while the azimuth of the gyroscope remains unaltered. The means whereby such energiza tion of motor |32 is accomplished will now be set forth.

A knob is carried at one end of a hollow shaft |36, rotation of which causes rotation of a first sprocket |31 connected by a sprocket chain |4| with a second sprocket |40. The latter sprocket is carried on a second hollow shaft |42, which also carries a pair of contact arms |43 and |44, insulated therefrom, and moving about the surface of a circular resistance member |45. The rotation of hollow shaft |42 is in the same sense as the rotation of knob |35. Arms |43 and |44 and resistance member |45 comprise a first potentiometer |40. Contact arms |43 and |44 are electrically connected to a pair of slip rings |46 and |41 carried by shaft 42 and insulated therefrom. A pair of brushes |50 and I5| are provided for making contact with slip rings |46 and |41, and electrical conductors |52 and |53 make electrical connection between brushes |50 and l5| and an amplifier |54. Amplifier |54 is provided with electrical energy from any suitable source of alternating current by conductors |55 and Resistance member |45 is tapped at four equally spaced points around its circumference as at |51, |60, |6I, and |62. For reasons presently to be set forth, resistance member |45 is mounted for rotation on a shaft |63, from which it is insulated, and taps |51, |60, |6I, and |62 are connected to a number of slip rings |64, |65, |66, and |61 carried by and insulated from shaft |63. A like number of brushes |10, |1|, |12, and |13 are provided for making electrical contact with slip rings |64, |65, |66, and |61, respectively, and are connected respectively by means of conductors |14, |15, |16, and |11 with similar taps |30, |6|, |82, and |83 of a similar circular resistance member |04 fixed with respect to housing 22. Cooperating with member |84 to comprise a second potentiometer |85 is a second pair of contact arms |66 and |81, carried by and insulated from shaft |33 of motor |32, and connected thereto are a pair of slip rings and |9I also carried by and insulated from shaft |33. A pair of brushes |92 and |93 cooperate with slip rings |60 and |9| and are connected by conductors |94 and |95 with amplifier |54. Motor |32 is connected with amplifier |54 by conductors |96, |91, and 200. It will thus be apparent that the comassenso 7 bination of potentiometers |40 and |35, together with motor |32 and ampliiier |54, comprise a multiple bridge type of telemetric system 215.

Potentiometers |43 and |35 comprise portions or an electrical bridge, When movable contacts |43 and |44 have a proper angular disposition on winding |45 compared with that of movable contacts and |31 on winding |34, the bridge is in balance: this is the normal condition of this bridge circuit. If, however, knob |35 is manually rotated by the bombardier, the relationship between the angular disposition of contacts |43 and |44 on winding |45 and that of contacts |05 and |31 on winding |34 is altered, and an alternating potential is impressed upon the input of amplifier |54 which is of one phase or the opposite phase, depending on the direction of displacement of contacts |43 and |44 from the position of bal: ance.

Amplifier |54 is of any suitable type wherein reversible actuation of avmotor is caused by energization of the amplifier input with signals of reversible phase. Such ampliers are well known in the art, and details of the structure of amplier |54 are therefore not included in the present application.

'I'he over all effect of this portion of our invention is therefore to cause housing 22 to rotate in a first direction with respect to shaft |5 when knob |35 is rotated in a first direction and in the opposite direction when the knob is rotated in the opposite direction.

The gear ratio between sprockets |31 and |40, and the number of teeth in worm wheel 23. are so chosen that the rotated displacement of housing 22 from its original position bears a selected ratio to the rotation of knob |35 to which it is due. In the preferred embodiment of our invention we make this a 1:1 ratio, and it will be obvious that a rotation of knob |35 through 15", for example, then produces rotation of housing 22 with respect to shaft I5 through the same angle, resulting in displacement of arm |32 to cause operation of the control surface of the craft. Arm |32 does not return to its normal position until the craft has changed its heading by the same angle; that is, by when the control surface is returned to its neutral position. Thus, a rotation of knob |35 in the preferred embodiment of our invention causes a change of equal magnitude in the course of the craft.

We have shown bombsight I2 as comprising a telescope 203 mounted for rotation about a normally horizontal axis 251, the latter being carried for rotation about a normally vertical axis in a ring gear 233. 'A pinion 20| is arranged in driving relation with ring gear 290 and is carried by a shaft 232 driven by motor 233. Shaft 232 also carries a worm 234 arranged in driving relation with a worm wheel 235 carried by a shaft 205. Electrical energy is provided to motor 253 by conductors 291, 300, and 30| from an amplifier 302, conductor 300 being grounded and amplifier 302 being supplied with electrical energy through conductors 303 and 304 from any suitable source of alternating current.

Mounted on shaft 205 and insulated therefrom are a pair of slip rings 305 and 305 connected to a pair of contact arms 301 and 3|0 also mounted on and insulated from shaft 235. y Brushes 3| and 3 I2 make contact with slip rings 305 and 305, and are connected by conductors 3|3 and 3|4 with amplifier 302.

Mounted on and insulated from shaft |53 is a third resistance member 3|5 which cooperates with movable contacts 301 and 3|! to comprise a third potentiometer 3|3. A number of slip rings 3|1, 320, 32|, and 322 are carried by and insulated from shaft |53 and make connection respectively with taps 323, 324, 325,V and 325, equally spaced around member 3|5. Electrical connection is made with slip rings 3|1, 320, 32|, and 322 by a like number of brushes 321, 330, 33|, and 332, and these in turn are connected to conduc tors 333, 334, 335, and 335.

Shaft |53 traverses hollow shaft |42 and carries on its outer end a gear 331 which cooperates through a pinion 340, a shaft 34|, a sprocket 342, a sprocket chain 343, and a sprocket 344, with a shaft 345 traversing hollow shaft |35, and carrylng at its outer end a second manually adjustable knob 345. It is thus apparent that rotation of knob 345 acts to rotate shaft |53 in the reverse sense which is exactly opposite to the effect of rotating knob |35, as far as potentiometer |43 is concerned.

Shaft 35 carries and is insulated from a pair of contact arms 341 and 350, and a pair of slip rings 35| and 352 are also mounted on and insulated from shaft 35, electrical connections being made between contacts 341 and 350 and slip rings 35| and 352 respectively. A pair of brushes 353 and 354 cooperate with slip rings 35| and maand are connected `by conductors 355 and 355 with amplider 302. Fixed with respect to contacts 341 and 350, and cooperating therewith to form a fourth potentiometer 351 ,is a resistance member 350 tapped at equidistant spaced points 35|, 352, 353, and 384 to which respectively are connected conductors 333, 334, 335, and 335. It will thus be apparent that the combination of potentiometers 3|5 and 351, together with motor 233 and amplifier 302, comprises a second multiple bridge type of telemetric system 355.

Potentiometers 3|5 and 351 comprise portions of an electrical bridge. When movable contacts 341 and 350 have the proper angular disposition on resistance member 350 compared with that of movable contacts 301 and-3|0 on resistance member 3|5, the bridge is in balance: This is the normal condition of this' bridge circuit. If however, the relationship between the angular disposition of contacts 301 and 310 on member 3|5 and that of movable contacts 341 and 350 on member 350 is altered, an alternating potential is impressed upon the input of amplifier 302, which is of one phase' or the other, depending on the direction of the relative displacement between the contactors of potentiometers 3|5 and 351.

Amplifier 302 is of any `suitable type wherein A reversible actuation of a motor is completed by energization of the input of the amplifier with signals of reversible phase. Such amplifiers are well known in the art and details of the structure of amplifier 302 are therefore not included in the present application.

It will be understood that if the craft diverses from a selected course, the line of sight of the telescope having previously been directed in a desired manner for flight alongv the desired course, the line of sight will be deflected from its proper alignment. While it is of course understood that return of the crait to its proper course will return the telescope to its proper alignment, nevertheless, it may be that during the time the craft has veered the bombardier should `be synchronizing in preparation for releasing a bomb. A departure of the line of sight from its correct alignment, even if of short duration, would seriously impede the bombardier in his attempts to synchronize. The speed of operation of motor 293 is so great, however, that it is capable of returning the telescope to a desired position under the control of amplifier 332 much more quickly than the craft can be returned to its desired course under the operation of operator I3I.

For this reason potentiometer 361 is made operable by shaft 36 whose operation controls the return of gyroscope I4 to its normal position. Veering of the craft causes resistance member 363 to rotate with respect to arms 341 and 353 which are stabilized by shaft I6 through gears I1, 43, and 31, giving these arms a different displaced arrangement with respect to the taps on member 351 from that held by contact arms 331 and 3I3 with respect to winding 3I5, A. C. input is thus provided to amplifier 332, energizing motor 293 to cause rotation of ring gear 233, at the same time causing rotation of arms 331 and 3I3 with respect to resistance member 3|5. The former rotation is in an opposite direction to the movement of the craft initiating it, so that the telescope returns to its desired azimuth setting. The latter rotation acts to rebalance the bridge 365.

Return of the craft from its deviated course to its desired course is accompanied by a tendency of gyroscope I4 to depart from its displaced position and therefore by a further rotation of resistance member 363, this time in the opposite direction to that which it took on departure of the craft from its course, and the telescope is turned with respect to the plane at the same rate as and in the opposite direction to the returning movement of the plane. movement of the plane in space a corresponding and opposite movement of the telescope is performed so that the target is at all times maintained in the same position in the field of the telescope. So sensitive is the bridge 365 and so rapid is the action of motor 293 that no perceptible change in the line of sight actually takes place.

The function of knob 346 will now be explained. As pointed out previously, it is desirable to control the movement of the craft by manipulation of the bombsight. If the target is out of range of the sight, in azimuth, and it is desired to bring the target into the sight, rotation of knob |35 is effective to cause turning of the craft through operation of motor |32, but through the operation of motor 293 under the influence of potentiometer 351 the line of sight is maintained in its original direction in space and is therefore generally no nearer the target than it was before the Plane was turned. Means must therefore be provided for influencing both motors |32 and 293 simultaneously to cause both the plane and the sight to rotate in azimuth in space in the same direction. This function is performed by knob 346 acting through shaft |63 upon both member |45 and member 3I5, causing them to rotate simultaneously in the same direction. Thus, both multiple bridges are unbalanced and motors |32 and 233 are energized to operate contact arms I86| B1 and 331-3I3 to rebalance the respective bridges. The direction of unbalance, however, is opposite to that brought about through the action of potentiometer 351 in the last example, so that the unbalance normally caused by potentiometer 351 responding to movement of shaft 35 is nullified by an equal and opposite unbalance caused by potentiometer 3|6 due to operation of knob 346, when the rates of operation of motors 34, |32, and 233 are properly selected.

Thus, for any azimuth Operation of knob 346 performs a secondary function in connection with synchronization in azimuth. It is well known to those familiar with the art of bombsights that if a craft flying with a wind having a cross component is continuously pointed at a target, the ground path of the craft is not a straight line toward the target, but rather a curve starting from the location of the craft at a given instant and ultimately approaching the target up-wind. It is found in practical applications of principles embodied in our invention that if, when a drift angle correction is inserted by use of knob |35, a displacement correction having a known proportion to the drift angle correction in terms of rotation of the several knobs is simultaneously put in by the use of knob 346, the curved path is thereafter reduced substantially to a straight line approach to the target, the proportion being of the order of 37 to 6. The ratio between gears 343 and 331 and sprockets 344 and 343 as compared to the ratio between sprocket wheels |31 and |43 is such as to provide this ratio between the effect of rotation of knobs |35 and 346.

Referring now to Figures 2 and 3, it will be apparent that taken together they comprise a wiring diagram of a complete system embodying our invention. In Figures 2 and 3, 366 refers generally to a power supply for the units comprising our system, 361 to a steering motor attachment, 31| to the Norden directional stabilizer, which is of known construction, and 312 to the Sperry bombsight, also of generally known construction but slightly modified for use in our system, and 313 to a control attachment.

Referring first to control attachment 313, examination will show that it is comprised of potentiometer |43, hereafter referred to as the steering leader potentiometer, potentiometer 351, hereafter referred to as the optics follower potentiometer, motor 293, hereafter referred to as the optics motor, a switch 313 and a set of six contacts 314, 315, 316, 311, 383, and 33|. I'he steering leader and optics follower potentiometers and optics motor have been previously described and their operative relationship with amplifiers |54 and 332, and so forth, has been pointed out.

One terminal of switch 313 is grounded as at 382. To the other terminal of switch 313 are connected a pair of conductors 333 and 334 leading to power supply unit 366. The set of six contacts is arranged and mounted for making connection with a similar set of contacts 335, 336, 331, 393, 39|, and 392 mounted in bombsight 312. Bombsight 312 further includes a three-phase gyrcscope motor 393, a D. C. constant speed motor 394 including a governor arrangement generally indicated at 395, and gyro erecting means 398, also of three-phase construction. A plurality of manually operable switches 391, 433, 43|, 432, and 459 also comprise a part of the bombsight as originally supplied. To the original equipment of the bombsight has been added a magnetic switch 433 and a manual switch 139 for a purpose presently to be set forth.

Directional stabilizer 31| comprises a. directional gyro motor 434, an erection cut-out switch 431, a torque motor 436, clutch solenoids ||5 and IIS, potentiometer 21, and optics leader potentiometer 3 I6. Steering motor attachment 361 comprises steering follower potentiometer I35 and steering motor |32.

Power supply unit 366 includes a battery 4I3 whose right hand terminal is positive as indicated, a single phase 120 cycle inverter 4I I, a three phase ll 400 cycle inverter 4|2, and a pairof magnetic switches 4l3 and 4|4.

In addition to the units thus described. the iigures show amplifiers 32. |54, and 302 and a. pair of switches 4|5 and 4|3. Switches 4I5 and 4|0 are normally located in the control panel of the automatic night control and are operated by the pilot of the craft. One side of each oi the switches is connected to the positive terminal 4|1 of battery 4|0 as by conductors 420 and 42| leading to a common positive bus bar 422.

Closing of switch 4|5 completes a circuit through a conductor 423 to the shunt wound direct current stabilizer gyro motor 404, the circuit being completed through a ground connection 424 at the gyro motor and a ground connection 425 to the negative terminal of the battery. Motor 404 is a shunt wound direct current motor. Closing of switch 4i5 completes a circuit through a conductor 426 to energize the shunt wound direct current torque motor 400. the circuit being completed through a ground connection 421 at the torque motor and ground connection 425.

One terminal of switch 401 is also connected to the positive terminal of battery 4|0 as by a conductor 430, conductor 42|, and positive bus 422. Closing of switch 401 completes a circuit through a conductor 43| to the erection cutout operator of the vertical gyro ofY the craft.

for a purpose having no bearing on the present invention. The circuit is completed through a ground connection at the erection cut-out operator and ground connection 420.

Closing of switch 401 also completes a circuit through a conductor 433 leading to terminal 314 of control attachment 310. When the control attachment is instaliedon the bombsight. connection is made as indicated by the dotted line between contacts 314 and 300. Contact 335 is connected as by conductor 434 with one terminal of the winding 435 of magnetic switch 403: The other terminal thereof is grounded as by conductor 430. Therefore, closing of switch 401 energizes magnetic switch 403 to open a pair of normally closed circuits through contact blades 431 and 440. The energizing circuit can be traced as follows: From Vthe positive terminalof the battery. bus 422, conductor 42|. conductor 430, switch 401. switch 100, conductor conductor 433. contact 314. contact 305. conductor 434, winding 435. ground connection 430, ground connection 425 and back to the battery. Interruption of the circuits through these contact arms acts to cut out the erection system of the bombsight in the same fashion as. and as a substitute for the system originally in the sight.

One end of the D. C. winding of three phase inverter 4I2 is connected with the negative terminal of battery 4|0 by conductor 431. The other end of the D. C. winding ofinverter 4|2 is connected to the positive terminal of battery 4|0 by conductors 440, 44|, 442. and 443, a circuit controlling arm 444 of magnetic switch 4I3 being included in series in this circuit. One terminal of the winding 445 0f magnetic switch 4I3 is connected to the positive terminal of the battery by conductors 440, 442, and 443. The other terminal of winding 445 is connected by conductor 333 with switch 313 in the control attachment. It is thus apparent that on closing switch 313 a complete circuit is formed from the positive terminal of the battery through conductors 443, 442, 446, winding 445. conductor 303, switch 313, ground connection 302, ground connection 425 back to the negative terminal oi the battery, thus energizing magnetic switch 4|3. Energization of switch 4|3 completes the circuit from the positive pole of the battery through conductors 443, 442, and 44|, arm 444, conductor 440, the D. C. winding of the three phase inverter, conductor 431 and back to the negative terminal of the battery.

Operation of the 400 cycle inverter is thus initiated by energization of magnetic switch-3, and three phase 400 cycle alternating current is provided through conductors 441, 450. and 45| to contacts 311, 300, and 30| of attachment 310, and thence to contacts 300, 30|, and 302, respectively in bombsight 312. In the bombsight, contact 300 is connected to one terminal of theA bombsight motor as by conductors 452. 453. and 454, blade 455 of switch 450 being provided for interrupting the circuit. Contact 30| is connected to a second terminal of the gyro motor by conductors 453, 451. and 450. blade 43| of switch 450 being provided for interrupting the circuit, and contact 302 is connected to the third terminal oi gyro motor 303 by conductors 452 and 403, no switch being provided in this circuit. When switch 450 is open. operation of motor 303 is interrupted since the supply of current to two of its phases is interrupted.

qontact 300 is also connected to a first terminal of the three-phase gyro erection device 305 by conductors 452 and 404. Contact 30| is also connected to a second terminal of the gyro erec tion system by conductors 453. 435, 405, and 451. switch 40| andyblade 431 of magnetic switch 403 being included in series in this circuit. Co tact302 is also connected to a third terminal of gyro erection system 303 by conductors 452I 410. 41|, and 412. switch 402 and contact arm 440 of magnetic switch 403 being connected ln sexies in this circuit. It will now be clear that on energization of magnetic switch 403 by closure of switch 401the Isupply of alternating current to the gyro erection mechanism 300 is cut oil.' by interruption of the-supply of two phases of the current for the erection means. It is also apparent that when magnetic switch 403 is not energized all three phases of the erection system are energized, subject to manual control of switches 40| and 402 which forms no part of this invention.

In the power supply one terminal of the three phase inverter is connecter to the negative terminal of battery 4|0. and therefore grounded as at 413. Terminal 30| is therefore connected not only with one phase oi the three-phase alternating current but alsowith the negative terminai of the battery. Terminal 315 in the control attachment is connected to the positive terminal of the battery by conductor 414. Connector 301 cooperating with connector 310 is connected to one terminal 415 of D. C. motor 305 by conductors 410 and 411. The other terminal 400 of motor 304 is connected to contact 300 by conductors 40|, 403', and 432. A circuit may therefore be traced from the positive terminal of the battery through bus 422, conductor 414l contact 316, contact 301. conductor 413, and conductor 411. to motor 305, thence by conductors 40|, 453', 462, contacts 302 and 30|, conductor 45|. and conductor 431, back to the negative terminal of the battery.

Switches 331 and 400 are shown as connected in series between contact 300 and 331 by conductors 432. 403, 404, and 410, but it will be observed that connector 315 cooperating with connector 300 is not used in the practice o! our invention. the function perfumed thereby in the original bombsight being otherwise accomplished.

One end of the D. C. winding of single phase inverter 4|| is connected with the negative terminal of battery 4|0 by conductors 435 and 431. The other end of the D. C. winding of inverter 4|| is connected to the positive terminal of battery 4|0 by conductors 433, 431, 430, and 443, the circuit contro! arm 43| of magnetic switch 4|4 being included in series in this circuit. One terminal oi' the winding 432 of magnetic switch 4|4 is connected to the positive terminal of the battery by conductors 433, 430. and 443. The other terminal of winding 432 is connected by conductor 334 with switch 313 in control attachment 310. It is thus apparent that on closing switch 313 a complete circuit is formed from the positive terminal of the battery through conductors 443, 430, 433, winding 432, conductor 334, switch 313. ground connection 352, and ground connection 425 back to the negative terminal of the battery, thus energizing magnetic switch 4 I4. Energization of switch 4|4 completes a circuit through the D. C. winding of the inverter which may be traced from the positive pole of the battery through conductors 443. 430, 451, contact arm 43|, conductor 405, the D. C. winding of the inverter, conductor 435 and back to the negative terminal of the battery. Operation of the single phase inverter is therefore initiated. by closing of switch 313. simultaneously with the initiation of operation of three phase inverter 4 I2.

It will be noted that one terminal of the single phase winding of inverter 4|| is connected to the negative terminal of the battery and to ground by conductor 434. The other A. C. terminal of the inverter is connected as by conductor 495 with input conductors 44, |55, and 303 of amplifiers 32, |54, and 302, respectively.

A ground connection 431 is provided and connected as by a conductor 500, to conductors 45, |55, and 304 of amplifiers 32, |54 and 302 respectively.

For a disclosure of the detailed structure of a preferred embodiment oi' our invention. reference is now made to Figures 4, 5, and 6 which disclose a control attachment built according to principles of our invention. Figure 5 is a continuation of Figure 4, and Figure 6 is a view showing portions broken away along the line generally indicated by 5-5 in Figure 4. Insofar as mechanical elements appearing in these iigures have appeared in figures previously described, the same reference numerals have been applied. In Figure 5 it will be seen that knob 345 is secured to shaft 345 by a set screw 502 and `that shaft 345 carries at the opposite end sprocket 344. Knob |35 is mounted on a spacing bushing, and the bushing is secured to shaft |35 by a set screw 504. Shaft |35 passes through a bushing 505 in the cover 505 of a housing 501, and an external shoulder 5I0 is provided on hollow shaft |35 for cooperating with the inner end of bushing 505. A bushing 5|| is provided in housing 501 for the sprocket end of shaft 345. The lower end of hollow shaft |36 carries through sprocket wheel |31. It will be seen that, when these parts are assembled as indicated in the diagram, hollow shaft |35 is maintained in proper axial relationship with shaft 345 by a shoulder 5|! provided on the latter. there being cooperation between bushing 503 and knob 345. The dimensions of bushing 505 are also calculated so that it cooperates with a hub 5|! on the under side of cover plate 505, with shou1- der 5|0 of hollow shaft |35, and with the lower edge of bushing 503 to suitably space and support the various parts. The first sprocket chain |4'I is operably associated with sprocket |31 to connect it with sprocket |40 i'lxed on a shaft |42. It will be noted that shaft |42 in the actual mechanical structure corresponds to hollow shaft |42 in Figure 1. since I have found it more convenient to mount the resistance windings on the hollow shaft and the contact member on the solid shaft traversing it. This is merely an interchange of function of the two shafts and the system is otherwise exactly as disclosed in Figure l. The second sprocket chain 343 lcooperates with sprocket 344 and sprocket 342 fixed on shaft 34|. A pair of rollers 520 and 52| suitably mounted are spring pressed against sprocket chains |4| and 343 respectively by a. bifurcated spring member 522 in order to maintain a proper tension in the sprocket chains and remove any undesirable slack between the operation of the manual knob and resultant movement of the driven sprockets. Shaft |4'2 is provided with a bushing 523 in cover plate 505 and shaft 34| is provided with similar bushings 524 and 525 in cover p-late 505 and housing 501 respectively. In addition to sprocket 343 there is also fixed on shaft 34| a gear 340 adapted for cooperating with a split anti-backlash gear 331 which is spun onto a hollow hub 530.

Gear case housing 501 is secured to potentiometer housing 535 by set screws 531 and a dowel 540 passing through a projecting boss 54| carried by housing 501. A cylindrical hollow projection 542 is provided on housing 535 to cooperate with a. cylindrical bore 543 in gear case housing 501 to accomplish this mounting function. A further bore 544 is provided in housing 501 to receive a bearing member 545 which is held in position by the cooperation between bore 544 and the upper surface of projection 542. Hollow shaft |63 is supported at its upper end in bearing 545. which is therefore suitably aligned with bearing 523 in cover plate 506 so that hollow shaft |42 is suitably supported with respect to hollow shaft |63.

Member 542 is provided at its inner end with a bore 545 to receive an axially operative spring washer 543 and a bearing member 541 roviding further support for hollow shaft |53. A bracket 550 is carried by housing 535 and a bushing therein provides a suitable bearing for shaft |42 at the end remote from sprocket |4'0. A member 552 is mounted on shaft |42 by a set screw 553 to perform the function of rotating the members indicated in Figure l by |44 and |43.

Hollow shaft |63 is externally splined at its lower portion 554, and mounted on this splined portion is an internally splined member 555 performing the functions of resistance members |45 and 3|5, together with slip rings |54, |55, |55, and |51 and 3|1, 320, 32|, and 322. The splined relationship between member 555 and shaft |53 permits comparatively free relative axial movement between the two, while at the same time preventing any angular play therebetween.

A bearing 558 in member 555 is provided to insure proper concentric relationship between member 555 and shaft |42 which traverses it and which engages the inner surface oi bearing 553. A second bracket 555 is carried by housing 535 and is bored as at 55| to receive a bearing 560.

A portion of bore 551 is threaded as at 56| to receive a threaded ring 562. adapted to bear against bearing member 555.

Clamped between bearings 565 and 541 by the action of ring 552 against washer 548 is a second hollow shaft 563 secured to yet another hollow shaft 554 by a set screw 556 for unitary rotation therewith. Shaft 563 carries worm wheel 295 and shaft 564 is externally splined near its lower portion as at 566 to receive the internally splined hub 551 of a member 510 generally performing the function of movable contacts 351 and 3| 5 and slip rings 385 and 306 as indicated in Figure l. The lower-most end of shaft 564 is threaded to receive a nut 51| which cooperates with a lock washer 512 to maintain member 515 securely pressed against n. shoulder 513 on shaft 564.

Supported by housing 535 are a pair of contact supporting blocks 514. Slots are provided in these insulating blocks to receive a plurality of contact brushes arranged for cooperating with the slip rings of members 552, 555, and 515. The brushes are numbered, corresponding to their functions in Figure l, as 3H, 3I2, 321, 330, 33|, 332, |15. |1|, |12, |13. |55, and |5|. The cooperating slip rings are indicated by reference numerals 355, 306, 3|1, 325, 32|, 322, |64, |65, |66, |51, |41, and |46, respectively. The contact arms carried by members 514 are securely clamped by the action of bolts 515 and nuts 516. Blocks 514 are fastened to housing 535 by screws 585 which pass through elongated slots 53| in blocks 514, so that the blocks are permitted a certain degree of axial adjustment with respect to the concentric shafts bearing the various slip rings.

Fastened to blocks 514 as by bolts 562 are wire clamping members 553 supporting the various conductors leading to the contact members in blocks 514. To avoid unnecessarily complicating the drawing, the numbers given to these various conductors in Figure 1 have not been reproduced in this gure.

A pair of bosses 684 project from the walls of the housing and are bored to receive fastening members which form a part of the bombsight to which this attachment is adapted to be connected. A further pair of bosses 585 also project from the wall of housing 535 to support an insulating member 555 carrying on its outer surface contact members 314, 315, 315, 311, 365, and 38|. The contact members are fastened to member 586 by suitable rivets 581. This mounting of the contacts is so arranged that when the attachment is assembled with the bombsight by means of members 554 and the cooperating members on the sight, the contact members mounted on member 556 make contact with cooperating contact members 365, 385, 381, 395, 39|, and 392 in the sight. A wire clamping member 590. similar to member 553, is provided to support the conductors leading to the various contact members on member 555: the wire clamping member is secured to member 555 by screws 59 I Switch 313 is mounted on the housing 535 in a readily accessible position, and apertures 592 and 593 are provided in a wall of housing 535 for the support of suitable electrical connecting devices for conducting electrical energy to the various electrical elements in housing 535.

The structure of members 552, 555, and 510 will now be considered in more detail. Member 555 is shown in Figures 1 and 8 to comprise slip rings |61, |55, |55, |64. spaced by separators 544, and slip rings 3`2. 32|, 320, and 3|1 also spaced by insulating separators 544. Slip rings |54 and 322 are spaced by an insulating separator 545. The slip rings and separators referred to are mounted on a pair of insulating hubs 545 and 541.

Figure 9 illustrates the structure of a slip ring, and it will be seen to comprise a disk 550 of electrically conducting material provided with four apertures 65| equally spaced Aaround the disk at equal distances from its center with three further apertures 552 equally spaced between pairs of apertures 65| at greater distances from the'center of disk 65|), and an inwardly projecting tongue 553 located between the remaining pair of apertures 55| and extending radially outwardly a distance greater than the distance to the center of apertures 552.

In Figure l0 it is disclosed that after the disk has been manufactured the tongue portion 653 is bent twice at right angles to take the conformation indicated at 656. It will be realized that four such disks can be placed in face to face relatlonship, with the tongue of each upper disk projecting through the apertures 552 in one or more of the asssociated disks, and it will also be appreciated that by the provision of four apertures 652 the projecting tongue of each disk may be insulated against contact with any portion of the other disks, the assembly being mounted in proper relationship by fastening members passing through apertures 652. It will also be appreelated that if the tongue members of the several disks are made of different lengths to allow for the thickness of the various plates and insulating spacers therebetween, the surfaces of the final bends in the various tongues will be co-planar. This construction is illustrated in Figure 4 in which the tongues of slip rings |54 and |56 are shown co-planar at the lower end of member 555 and the tongues of slip rings 3|1 and 32| are shown as co-planar at the upper ends of member 555.

Referring now to Figure 8, it will be seen that an end view of member 555 as seen from the right is there presented. In the broken away portion of this figure, it will be seen that the face of hub 641 is recessed to receive a ring 555 of electrically resistant material, for example, sheet Nichrome, the latter being provided with inwardly projecting tabs 556. A ring 551 is provided with screws 550 threadedly engaging hub 541 for clamping ring 555 against the face of hub 541, the inner surface of ring 551 being coated with an insulating varnish to prevent electrical contact between the two rings. It may be assumed that the portion of ring 551 broken away in Figure 8 may be that overlying the tongue 553 of slip ring 3|1, said tongue being shown as emerging from an aperture 552 in hub 641 corresponding to the aligned apertures in disk 655. It is of course understood that spacers 644 are also provided with apertures adapted to align with the apertures 55| and 652 in disks 655 and hubs 645 and 541.

In Figure 8 there are also illustrated the heads of a set of rivets 65| traversing the apertures 65| in hubs 546 and 641 and spacers 544 and 645. The rivets cooperate with washers 642 and when tightly set down unite the hubs, slip rings, and separators into one unitary assembly to which resistance ring 655 and clamping ring 551 are assembled at one end. It will be understood that a similar arrangement is found at the other end of member 555 where a second resistance ring 652 is held in place by a clamping ring 553 as shown in the fragmentary broken away portion of Figure "I.

Figure '1 also shows the cooperation between member 655 and member 652, the same cooperation being understood to prevail at the other end of member 556 with member 510. Member 652 is constructed in a fashion generally similar to member 656. A hub 664 of insulatingmaterial is perforated for the passage of assembling members 666 and contact making rivets 666 and 661. Hub 664 is arranged in a fashion similar tc hub 641 to support a pair of slip rings |46 and |41 separated by a spacer 610. A set screw 61| is provided in the end of hub 664 for fastening it to shaft |42 which it is bored to receive. It will be remembered that member 555 is provided with internal splines as indicated in Figure 1 for cooperation with external splines on hollow shaft |63.

Mounted on hub 654 by rivets 666 is a spring arm |43. Rivets 666 make electrical connection between spring arm |43 and slip ring |41. In the same fashion, rivets 661 make electrical connection between slip ring |46 and a second spring arm |44. Resistance ring 562 performs the function of member |45 in Figure 1 and it is arranged that when members 552 and 655 are in their appropriate axial relationship, arms |43 and |44 will contact ring 662 at diametrically spaced points.

By the structure just described, it will be seen that relative rotation between member 552 and member 555 causes movement of contact arms |43 and |44 around resistance member 662 to perform the function recited in connection with Figure. l.

Referring now to Figure 6, it will be seen that worm 294 is carried on a shaft 292 driven by motor 293 and bearing on its outer end the male portion 594 of a coupling arrangement adapted to transmit rotation of shaft 292 to a gear in the bombsight referred to by reference numeral 29| in Figure l. Member 594 is secured to shaft 292 by a set screw 595.

Shaft 292 is supported on a pair of bearings 596 and 591 in a gear case housing 600 associated with motor 293. Housing 600 is provided with a hollow cylindrical projection 502 adapted to be received in a circular aperture 603 in housing 536 in such a position that worm 294 engages worm wheel 295. Shaft 292 is provided with a shoulder 664 and projection 602 is provided with a shoulder 505 between which bearing `595 is received. Housing 500 is secured to housing 536 by a number of screws 606.

Secured to housing 600 by suitable means is a plate 601. Mounted in a bore in plate 601 is a cup-shaped member 6|0 adapted to receive bearing 591. Bearing 591 is pressed against a shoulder 6|2 on shaft 292 by means of a spring washer 6|3 acting between washers 6I4 and 6|5, the latter being prevented from moving axially of shaft 292 by a snap ring 6|6 engaged in a groove 6|1 near the end of shaft 292. Axial movement of shaft 292 and its various bearing members is therefore substantially prevented.

Fixed to shaft 292 by a suitable hub 620 is a gear 62| which engages a pinion 622 carried on the rotor shaft 623 of motor 293. Shaft 623 passes through a bearing 624 in plate 661, and is spring pressed in a direction toward pinion 522 by conventional mechanism in a central hub 525 provided at the end of the housing 626 of motor 293. A gasket 621 is provided between 526 of motor 293 and gear case 660. and the whole assembly is maintained in oil tight relationship by screws 606.

Securely fixed to shaft 623 as by a bushing 636 is a squirrel cage rotor 63| adapted to cooperate with a set of held windings 632 mounted in housing 626. Field windings 632 are maintained in position in the housing through the agency of a split ring 533 engaged in a suitable recess 634 in housing 626 and pressing against spacers 635.

Also ilxed upon shaft 623 in a hub 636 to which is fastened by means of rivets 631 a friction member 640 adapted to cooperate with the dat surface 64| of bearing 624 for the purpose of minimizing hunting in the operation of motor 293.

Motor 293 an gears 62| and 622 are lubricated by a supply of oil maintained in housing 626 and gear case 600. For this reason a number of passages not shown are provided through plate 561, and oil pads 642 and 543 are provided to conduct lubricant by capillary action to points where lubrication is necessary. To prevent the passage of oil from gear case 600 into housing 535, an oil seal bearing has been selected for use in the position indicated at 596.

The effect of friction member 640 in reducing hunting in the motor may be explained as follows. Member 640 is made of Bakelite and member 624 is made of bronze. It has been found that when these two members are mounted for frictional engagement as disclosed herein under spring pressure as provided from hub 625, and suitably lubricated the friction between the members is much greater at very low speeds of rotation than it is at normal speeds of rotation. Thus the frictional effect of these two members is much greater in proportion at low motor speeds than at high motor speeds, and accordingly when the supply of electrical energy to the motor is interrupted and the speed of the motor falls off, it is brought to rest much more quickly by the use of these members than would occur if such members were not provided.

From the disclosure just recited, it will be obvlous that the function of our control attachment is that performed by elements indicated within the dotted line I3 in Figure l. It is obvious that for a complete system this control attachment must also cooperate with a directional stabilizer as indicated at in Figure 1, which includes generally known structure, together with certain new motor drive and resistance pickup attachments Whose mechanical structure will now be set forth in detail,

Our steering motor attachment is shown in Figures 1l. 12, and 13 to comprise a housing 22 bearing at one end potentiometer and at the other end motor |32. A section taken aong the line |2-I2 of Figure 1l is shown in Figure l2, and in this figure numeral |5 refers to the stabilized shaf t of the directional stabilizer. Mounted on shaft I6 by an internally threaded member 515 cooperating with threads on shaft I6 is a hollow shaft 615. Worm wheel 23 is rotatably mounted on hollow shaft 516 and is maintained in frictional engagement therewith by friction element 20. A spring 511 maintains expansive force between a collar 560 and a shoe 66| which engages friction member 20. Shoe 66| is secured against rotation with respect to hollow shaft 616 by a key 662. Collar 660 is prevented from axial movement along hollow shaft 616 under the influence of spring 611 by any suitable means such as snap ring 663 fitting in an external groove in hollow shaft 516 and engaging the collar. Thus it will be seen that frictional engagement between worm wheel 23 and shoe 66| is provided by member 20, and that if the rotational force between members 23 and 68| is sufficiently large, relative motion may take place therebetween.

Hollow shaft 616 is mounted for rotation within a cylindrically eccentric adjusting bushing 333 by a pair of bearings 334 and 335. A clamping ring 681 is provided to maintain hollow shaft 313. bushing 636 and bearings 334 and 333 in the proper relationship, and suitable sealing rings 330 and 63| are also provided.

Bushing 636 is rotatably adjustable in housing 31| for the purpose of providing proper lnterdlgitation between worm |54 and worm wheel 23. and a clamping ring 632 is provided with suitable bolts 633 for fixing the rotated relationship between bushing 636 and housing 61|. From the structure just recited, it will be seen that on rotation of shaft |6 the entire housing is caused to rotate about the same axis. carrying with it the potentiometer, motor, and so forth. It will also be apparent that, providing the tension of spring 311 is suitably selected, rotation of worm wheel 23 may take place even when shaft i3 is prevented from rotating, by taking advantage oi the slip friction introduced by the provision of member between members 23 and 63|.

Referring now to Figure 11, it will be seen that worm wheel 23 is actuated by motor |32 through worm |34 carried on shaft |33 driven by motor I 32. Shaft |33 is supported in suitable bearings 334 and 695 held by threaded ring 636 and split ring B31 in a pair of bored bosses 100 and 10| rising out of housing 22. A pair of spacing collars 102 and 103 are mounted on shaft |33 to maintain it in the proper axis relationship for satisfactory engagement between worm |34 and worm wheel 23.

As indicated in Figure 1, housing 22 is provided with locking arm 2| for engaging with a locking mechanism carried by the directional stabilizer. It is also provided with arm |30 carrying a mechanical linkage |21 for transmitting rotation of housing 22 about the axis of shaft I6 into control of the course of the craft. Housing 22 furthermore carries a pivot 104 to which may be connected a link 105 adapted to provide stabilization of a bombsight or other device whose azimuth is to be controlled,

One end of the shaft |33 carries a female connection 106 adapted to cooperate with a male connection 101 driven by motor |32 for actuation of r worm |34. The other end of shaft |33 projects through a flange 1|0 in housing 22 to operate the sliding contacts of potentiometer |33, best shown in Figures l1 and 13. The potentiometer is shown in section in Figure 11, the section being taken along the broken line l1|1 o1' Figure i3. It will be seen that the potentiometer is contained between flange 1|0 and a housing 1|| fastened thereto as by screws 1 I 2.

The potentiometer comprises a short cylindrical insulating member 1|3 fastened to flange 1||| by suitable means as by screws 1|4. Fastened to the cylindrical face of member 1|3 by a suitable means as by screws 1li are a pair of contact members 113 and 1|1 adapted to make contact respectively with a pair of slip rings 120 and 12| suitably mounted as by insulating members 122 and 123 on a hub 124 ilxed by a pin 123 to shaft |33. A pair of contact arms 123 and 121 carried by insulating member 122 and connected respectively to slip rings 120 and 12| are arranged to make sliding contact with a resistance ring 130 clamped to member 1I3 by a clamping ring 13 I.

Conducting studs 132 traverse member 1l3 at points radially and circumferentially spaced to cooperate with the tabs 333 of resistance ring 130 to which they are welded, and suitable channels such as 133 are provided for making electrical connection with these studs. An aperture 134 is provided in flange 1|'0 so that a multiple conductor cable may pass through for making connections to the four tabs of resistance ring 130 and to contact members 1l3 and 1|1.

From the structure above set forth, it will be seen that when shaft |33 is rotated, a change in the angular dispositionI of contacts 123 and 123 with respect to the tabs on resistance ring 130 takes place. thus affecting the electrical circuit in which potentiometer |35 is inserted. It will also be seen that rotation of housing 22 about the axis of shaft I3 as a unit causes no displacement of contacts and 123 with respect to ring 130. The section indicated in Figure 13 is taken along the`line |3-|3 in Figure 11, and Figure 13 also shows a cover 133 arranged to cooperate with housing 22 to enclose the gear and slip friction mechanism and protect it from dirt and mechanical mistreatment.

A second flange 133 is provided on housing 22 for supporting motor |32 which drives through a gear reduction 131, a stub shaft 1|3 carrying male connection 101.

In Figure 1 we have shown schematically that a potentiometer is mounted in association with the directional stabilizer for stabilization by shaft 35. Details of the embodiment of this portion of our invention are given in Figure 14 which discloses my potentiometer together with associated portions of the directional stabilizer. In this figure gyroscope i4 is shown as mounted in gimbal ring |-5 in a housing 333. The gimbal ring rotates about a vertical axis not included in the fragmentary showing in Figure 14, and carries concentric with this axis the ring gear Mounted on housing 333 of the directional gyroscope is the housing 334 of servomotor 34. The end of shaft 33 of servomotor 34 is formed as a pinion 335 engaging the gear 333 carried on a shaft 331. Pinion 330 thereon meshes with one of a pair of gears 33|. only one of which appears in the sectional view in Figure 21. As previously pointed out, motor 34 and therefore gears 33| are in continuous operation during use of the directional stabilizer.

Cooperating with the face of each gear 33| is a clutch member 332 operatively unitary with a gear 31. Engaging with both gears 31 is a gear 333 carried on a common shaft 334 with a second gear 335: Gear 3-35 meshes with .gear I1 on the gimbal ring I5 ofthe directional gyro. In the normal condition of the servomotor. neither of clutch members 332 is in engagement with its opposed gear 33|. It will be realized that since one of gears 33| meshes with pinion 330, and that the second of gears 33| meshes not with the pinion but with the first gear, it follows that gears 31 are urged in opposite directions when their respective clutches engage gears 33|. Therefore when one of the clutch members is brought into frictional engagement with a cooperating gear member by electromagnetic means which do not appear in this section, torque is applied to ring gear |1 in one direction or the other depending on which of the members was actuated.

In the practice of our invention, shaft 334 is extended and carries at its upper end a gear 333 adapted to cooperate with a second gear 333 carried on the shaft 331 of potentiometer 351. 

